The goal of the proposed research is to determine how information is represented, transformed and distributed by the collective activities of a group of neurons and used to control behavior. These processes must be defined to establish the existence of an ensemble neural code. The neural and muscular systems controlling the crayfish claw will be studied because variables of interest can be monitored, controlled and related directly to the animal's behavior. Interactions among sensory receptors, interneurons and motor neurons, during both active and imposed dactyl movements, will be studied using intracellular recording techniques, cross-correlation analysis, and other statistical methods for spike train analysis. Experimental approaches to be used will permit both the detection and measurement of physiological processes that underlie the conversion of information carried by an ensemble of proprioceptors to sequences of action potentials in a defined population of motoneurons. A spike train playback technique will be used to define the separate and collective behavioral influence of the motor neuron action potentials free from other variables such as previous activation history and the mechanical properties of the muscles. A movement playback technique will be used to dissociate central and peripheral (sensory) influences upon the motor neurons and to determine whether and by what mechanisms a given sensory "message" may be interpreted in more than one way, i.e. produce different action potential sequences and temporal relationships among the motor neuron spike trains.